The present specification relates to a network including snooping which may be DHCP (Dynamic Host Configuration Protocol) snooping.
DHCP snooping can be provided in a network to monitor and hence control the network in a variety of ways, and in particular to control illegitimate use of the network and to control QoS (quality of service) access of devices to the remainder of the network.
Many large organizations, such as corporations, universities, schools, libraries have large computer networks which allow ready physical access to the network by members of the public or students or employees or contractors. It is clearly desirable to control the access of individuals to the network both to prevent unauthorized action by the user and to provide more simple and efficient access to the network.
Thus, for example, it is desirable to prevent someone in such an environment attaching their computer to the network, for example in a docking station and taking control of the network in an undesirable manner. Such a user might try to use an unauthorized, IP address which would deny access to someone else with the same IP address. They might try to flood the network with undesirable data. They might also use the network to gain access to other devices, and they might try to take control of the servers of the network.
Furthermore, some types of device, for example IP phones, require a different type of service to a computer and it is useful to be able to determine whether a phone or a computer is connected to a network at a particular port and to appropriately direct the traffic to a further particular port.
WO 2004/042999 (Ericsson) discloses a method and arrangement for preventing illegitimate use of IP addresses in which when a subscriber requests an IP address it is checked that it is a DHCP message with valid subscriber values and a message from the subscriber with a false IP addresses is discarded by a filter.